The present invention relates to improvements in apparatus for testing cigarettes or analogous rod-shaped articles which constitute or form part of smokers'0 products. More particularly, the invention relates to improvements in apparatus for testing cigarettes or analogous rod-shaped articles (hereinafter referred to as cigarettes) during transport by a rapidly advancing conveyor, such as a rotary drum-shaped conveyor which rotates about its axis and is provided with peripheral flutes or analogous receiving means wherein the cigarettes are held in parallelism with the axis of the conveyor during travel toward, through or past and beyond a testing station.
It is known to test cigarettes or analogous rod-shaped articles of the tobacco processing industry by causing streams of air or another gaseous testing fluid to flow radially through the wrappers of successive cigarettes and by monitoring the pressure differential between the interior and the exterior of the wrappers. It is also known to test the wrappers of cigarettes for integrity by monitoring the pressure of testing fluid which is admitted into one end of the wrapper, by monitoring the pressure of fluid (if any) which issues from the other end of the wrapper, and by ascertaining the differential between the pressures of the inflowing and outflowing fluids. The testing fluid can be caused to flow through the wrappers of successive cigarettes by suction, or at least one end of the wrapper of the cigarette at the testing station can be connected with a source of compressed gaseous testing fluid.
As a rule, the wrappers of cigarettes are tested in the manufacturing machine itself or in a machine which processes the cigarettes, for example, in a filter tipping machine wherein plain cigarettes are joined with filter mouthpieces to form therewith filter cigarettes of unit length or multiple unit length. The testing can involve attempts at detection of open seams, holes, frayed ends of the wrappers, a combination of such defects and/or a monitoring of the porosity of intentionally perforated portions of the wrappers of plain cigarettes or filter cigarettes, namely, of wrapper portions which are perforated for the purpose of admitting relatively cool atmospheric air into the column of hot tobacco smoke. Many manufacturers of cigarettes demand the utilization of perforated wrappers because they believe that the admission of cool atmospheric air exerts a beneficial influence upon and reduces the presumably deleterious effects of tobacco smoke upon the health of the smoker. In many instances, the testing operation involves admission of compressed testing fluid (normally air) into both ends of a cigarette and monitoring the drop of pressure (if any) which develops as a result of escape of some testing fluid through the wrapper of the tested article. The differential between the pressure of the admitted testing fluid and the pressure of testing fluid in the interior of the wrapper of a cigarette at the testing station is indicative of the quality or condition of the tested article. The signals which are generated to denote the detected pressure differential are evaluated and, if warranted, utilized to segregate defective articles from satisfactory articles prior to entry of defective articles into the next machine, such as a packing machine which normally follows a filter tipping machine. The testing of filter cigarettes in a filter tipping machine is further indicative of the condition of the uniting band which is utilized to couple the filter mouthpiece with the tobacco-containing portion, e.g., with a plain cigarette. If the sealing action of the uniting band is unsatisfactory, excessive quantities of testing fluid will escape in the region where the plain cigarette abuts against the adjacent end portion of the filter.
Cigarettes are tested while advancing at the operating speed of a making or processing machine. The output of such machines is extremely high; for example, a modern filter tipping machine can turn out well in excess of one-hundred filter cigarettes per second. Therefore, the intervals which are allotted for the testing of individual cigarettes in a filter tipping or an analogous machine are extremely short, normally in the range of a few milliseconds. During such extremely short intervals, the pressure of testing fluid which is admitted into the interior of a cigarette at the testing station must be built up at both ends of the cigarette, and the signal denoting the drop of pressure as a result of porosity or defectiveness of the wrapper must be generated within the same short interval of time, namely, before the pressure of testing fluid is reduced again and not later than when the freshly tested cigarette advances beyond the testing station.
Each application and termination of pressure of testing fluid entails oscillations of the column of testing fluid in the form of standing waves in the conduits for testing fluid. Such oscillations of testing fluid are highly likely to distort the results of the testing operation. Therefore, the testing of a preceding cigarette must be followed by an interval which is long enough to allow the oscillations to fade out, i.e., the column of testing fluid in the conduit or conduits leading to and from the testing station must cease to oscillate before the transducer which converts pneumatic signals into electrical or other suitable signals for further processing generates a signal denoting the condition of the tested article. This entails considerable shortening on the aforediscussed extremely short intervals of time which are available for the testing of successive cigarettes during transport through the testing station in a modern high-speed cigarette making or processing machine. The shorter the intervals which are available for actual testing, the greater is the likelihood of distortion of signals which denote the condition of the tested articles. Furthermore, the aforediscussed shortening of extremely short intervals which are available for testing of successive cigarettes, namely, a shortening for the purpose of permitting the oscillations of testing fluid to disappear, reduces the possibility of further increasing the output of the machines in which the testing apparatus are used. In other words, if all other units of a machine for the making or processing of cigarettes would allow a pronounced increase of the output, for example, to 10,000 cigarettes per minute, presently known testing apparatus would prevent such increase in output because their operation at corresponding speeds of the articles to be tested would be unsatisfactory so that they would permit defective cigarettes to reach the next processing station and/or would or could cause ejection or segregation of satisfactory cigarettes.